SECURITIES - Available for Sale Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Available for sale:
Less than 12 months, Estimated Fair Value	$ 99,812	$ 236,848
Less than 12 months, Gross Unrealized Losses	(779)	(2,666)
Greater than 12 months, Estimated Fair Value	424,638	481,253
Greater than 12 months, Gross Unrealized Losses	(16,685)	(13,627)
U.S. GSE securities
Available for sale:
Less than 12 months, Estimated Fair Value	0	0
Less than 12 months, Gross Unrealized Losses	0	0
Greater than 12 months, Estimated Fair Value	29,050	56,815
Greater than 12 months, Gross Unrealized Losses	(947)	(1,180)
State and municipal obligations
Available for sale:
Less than 12 months, Estimated Fair Value	6,655	35,350
Less than 12 months, Gross Unrealized Losses	(15)	(301)
Greater than 12 months, Estimated Fair Value	21,273	28,165
Greater than 12 months, Gross Unrealized Losses	(339)	(518)
U.S. GSE residential mortgage-backed securities
Available for sale:
Less than 12 months, Estimated Fair Value	0	107,408
Less than 12 months, Gross Unrealized Losses	0	(1,153)
Greater than 12 months, Estimated Fair Value	88,762	69,571
Greater than 12 months, Gross Unrealized Losses	(3,036)	(1,680)
U.S. GSE residential collateralized mortgage obligations
Available for sale:
Less than 12 months, Estimated Fair Value	46,452	77,705
Less than 12 months, Gross Unrealized Losses	(141)	(759)
Greater than 12 months, Estimated Fair Value	172,468	224,932
Greater than 12 months, Gross Unrealized Losses	(5,813)	(6,257)
U.S. GSE commercial mortgage-backed securities
Available for sale:
Less than 12 months, Estimated Fair Value	0	2,345
Less than 12 months, Gross Unrealized Losses	0	(40)
Greater than 12 months, Estimated Fair Value	3,508	0
Greater than 12 months, Gross Unrealized Losses	(28)	0
U.S. GSE commercial collateralized mortgage obligations
Available for sale:
Less than 12 months, Estimated Fair Value	46,705	452
Less than 12 months, Gross Unrealized Losses	(623)	(1)
Greater than 12 months, Estimated Fair Value	43,933	48,264
Greater than 12 months, Gross Unrealized Losses	(1,916)	(1,248)
Other asset backed securities
Available for sale:
Less than 12 months, Estimated Fair Value	0	0
Less than 12 months, Gross Unrealized Losses	0	0
Greater than 12 months, Estimated Fair Value	23,219	23,401
Greater than 12 months, Gross Unrealized Losses	(1,031)	(849)
Corporate bonds
Available for sale:
Less than 12 months, Estimated Fair Value	0	13,588
Less than 12 months, Gross Unrealized Losses	0	(412)
Greater than 12 months, Estimated Fair Value	42,425	30,105
Greater than 12 months, Gross Unrealized Losses	$ (3,575)	$ (1,895)